CN115366864A - Motor Vehicle Brake Friction Pad Loss Monitoring System - Google Patents

Abstract

The present application relates to a motor vehicle brake pad wear monitoring system, wherein the motor vehicle comprises a brake device acting on each wheel thereof, the brake device having a pad that is non-rotatable relative to the wheel but linearly displaceable parallel to the axis of rotation of the wheel, the motor vehicle further comprising a hydraulic brake drive device having a linearly displaceable brake piston for acting on the pad to generate a braking force for the wheel, and a brake fluid reservoir in fluid communication with the hydraulic brake drive device, the method comprising: stopping the motor vehicle in a horizontal or substantially horizontal attitude; determining a current liquid level in the brake fluid storage tank; determining a volume change amount of brake fluid in the brake fluid storage tank based on a previously determined reference level and the current level; in the case where the wear thickness of the friction plate provided for the front wheel or the rear wheel is known, the wear thickness of the friction plate provided for the rear wheel or the front wheel is determined by the volume change amount of the brake fluid in the brake fluid storage tank and the diameter of the brake piston of the brake device.

Description

Motor Vehicle Brake Friction Pad Loss Monitoring System

technical field

The present application basically relates to a system for monitoring wear of brake pads of a motor vehicle.

Background technique

The brake system is a mandatory device on motor vehicles according to the requirements of road traffic regulations. The brake device mainly includes a brake disc mounted rotatably together with the rim of the wheel and a friction disc mounted immovably relative to the rim. For each brake disc, the friction plates are, for example, two friction plates, which are installed on opposite sides of the corresponding brake disc with a certain gap, and driven by the drive mechanism, they can move to contact the rotating brake disc and apply clamping force to it. tightening force so that the brake disc stops due to friction braking.

Generally, the hardness of the brake disc is higher than that of the friction lining. Therefore, the thickness of the friction plate will wear and thin with long-term braking. In order to ensure that sufficient frictional braking force can be generated, it is necessary to replace the new friction plate in time after the loss of the friction plate is reduced to a certain extent. In this way, it is necessary to monitor the wear and tear of the friction lining.

A traditional friction lining wear monitoring method is to arrange a metal sheet on the back plate of the friction lining, and the metal sheet has a free end adjacent to the wear surface of the friction lining (that is, the surface in contact with the brake disc), At the same time, the free end retreats a certain distance from the wear surface in the thickness direction of the friction plate. Under normal conditions, the free ends of the metal plates are spaced from the disc when the pads are in contact with the disc for wheel braking. However, when the wear of the friction plate is reduced to a certain extent and then the wheel is braked, the free end of the metal plate will contact the rotating brake disc and make a sharp noise, reminding the driver that a new friction plate needs to be replaced. The disadvantage of this friction lining wear monitoring method is that the driver cannot perceive the wear degree of the friction lining before the sharp noise is produced. In addition, the frictional contact of the metal plate with the brake disc can cause damage to the brake disc.

Another traditional way of monitoring friction lining loss is to equip the friction lining with a resistive sensor. For example, such resistive sensors can be directly buried in the friction material of the friction pad or inserted into the back plate of the friction pad and distributed along the thickness direction of the friction material. When the friction plate is thinned to a certain extent due to loss, the resistance value of the resistive sensor changes during the braking process, so the alarm can be predicted by detecting this resistance value change. However, the disadvantage of this friction plate loss monitoring method is that a special cable must be provided for the resistive sensor, so as to ensure the reading of the electrical signal. However, the existence of cables increases the difficulty of the overall structure design and assembly of the suspension. In addition, such a resistive sensor cannot provide the driver with monitoring of the continuous wear level of the friction lining. Therefore, the resistive sensor and its cable will lead to an increase in component costs, design and assembly costs.

Therefore, in order to reduce design and assembly costs, it is necessary to use less or no resistive sensors and be able to monitor the degree of wear of the brake friction pads.

Contents of the invention

In view of the above problems, the present application aims to propose a novel friction lining wear monitoring system and method, so that the wear conditions of the friction linings equipped on all wheels of a motor vehicle can be basically determined without or with fewer additional sensors.

According to one aspect of the present application, there is provided a method for monitoring wear of brake pads of a motor vehicle, wherein the motor vehicle includes a braking device acting on each wheel thereof, and the braking device has a non-rotatable However, friction plates that can move linearly parallel to the axis of rotation of the wheel, the motor vehicle also includes a hydraulic brake drive and a brake fluid storage tank in fluid communication with the hydraulic brake drive, the hydraulic brake drive Having a brake piston movable linearly to act on the friction lining to generate a braking force against the wheel, the method comprising:

Stop the motor vehicle in a horizontal or substantially horizontal posture;

determining the current fluid level in the brake fluid storage tank;

determining the brake fluid volume change (ΔV _L ) in the brake fluid storage tank based on the previously determined reference fluid level and the current fluid level;

In the case that the wear thickness of the friction lining equipped for the front wheel or the rear wheel is known, the volume change of the brake fluid in the brake fluid storage tank, the diameter of the brake piston driven by the hydraulic brake To determine the wear thickness of the friction plate equipped for the rear wheel or front wheel accordingly.

Optionally, when the wear thickness of the friction lining equipped for the front wheel or the rear wheel is known, the following formula is used to determine the wear thickness of the friction lining equipped for the rear wheel or the front wheel accordingly,

ΔL _X ＝(ΔV _L -πD ₀ ² ·ΔL ₀ -γ)/(πD _X ² ), where ΔL _X is the wear thickness of the friction lining to be determined, D ₀ is the friction lining corresponding to the known wear thickness The diameter of the brake piston, D _X is the diameter of the brake piston corresponding to the friction plate to be determined, ΔV _L is the volume change of the brake fluid in the brake fluid storage tank, and γ is a non-zero empirical constant.

Optionally, the reference liquid level is the liquid level in the brake fluid storage tank when the thickness of the new friction plates of the same motor vehicle or all the friction plates of the same motor vehicle is known and the vehicle is stopped in a horizontal or substantially horizontal posture. bit.

Optionally, no additional brake fluid is added to the brake fluid storage tank after the reference fluid level is determined and before the fluid level in the brake fluid storage tank is determined again.

Optionally, a resistive sensor is arranged in the friction plate with known wear thickness to determine the wear thickness of the friction plate.

Optionally, an electronic parking brake (700) or an electromechanical brake (710) is configured for the friction lining with known wear thickness, so as to determine the wear thickness of the friction lining.

Optionally, the electronic parking brake or the electromechanical brake includes a driving motor and a piston driving member that is driven by the driving motor and can move linearly, and the braking piston is suitable for being driven by the piston when the motor vehicle is braking. The component is driven to contact the friction plate, thereby driving the friction plate to move.

Optionally, after the motor vehicle has been parked, the drive motor is operated to move the piston drive member to a predetermined reference position;

Operating the drive motor again to move the piston driver from the reference position to its stop position in contact with the brake piston, wherein the stop position corresponds to the parking brake of the brake piston location correspondence;

determining a distance between the reference position and the stop position;

The determined distance is compared with a previously determined reference distance to determine the wear thickness of the tested friction plate as the known wear thickness.

Optionally, the reference distance is determined when the thickness of the tested friction lining is known or the tested friction lining is a brand new friction lining and when the parking brake is performed. The distance to move to the stop position.

Optionally, the known wear thickness of the tested friction plate is the absolute value of the difference between the determined distance and the reference distance.

Optionally, after the wear thickness of any tested friction plate is lower than a predetermined value, the driver of the motor vehicle is reminded to replace the tested friction plate.

Optionally, the electronic parking brake or the electronic mechanical brake further includes a deceleration mechanism connected to the output shaft of the driving motor, and a linear movement mechanism driven by the deceleration mechanism, and the deceleration mechanism can provide It has a locking function to prevent the piston driving part from moving freely, and the piston driving part can move linearly by being driven by the linear moving mechanism through the driving motor.

Optionally, the linear movement mechanism is a threaded screw structure, the threaded screw structure includes a mandrel connected to the output shaft of the reduction mechanism, and the outer surface of the mandrel is formed with external threads, the The piston driving member is a threaded member, has an internal thread engageable with the external thread, does not rotate when the mandrel rotates, and can linearly move back and forth along the axial direction of the mandrel.

Optionally, the distance between the reference position and the stop position depends at least on the rotational speed of the drive motor, the transmission ratio of the reduction mechanism, the lead screw pitch of the threaded screw structure and the drive motor power-on time.

Optionally, before performing the determination of the known wear thickness, the hydraulic brake driving device is used to apply parking brake to wheels not equipped with the electronic parking brake.

Optionally, the moving direction of the piston driving member to the reference position is opposite to the moving direction of the piston driving member from the reference position to the stop position.

According to another aspect of the present application, there is also provided a motor vehicle brake pad loss monitoring system, wherein the motor vehicle includes a braking device acting on each wheel thereof, and the braking device has non-rotatable but linearly movable friction plates parallel to the axis of rotation of the wheel, the motor vehicle also includes a hydraulic brake actuator and a brake fluid storage tank in fluid communication with the hydraulic brake actuator, the hydraulic brake actuator The driving device has a brake piston that can move linearly to act on the friction plate to generate a braking force against the wheel. The system includes:

a liquid level sensor configured in the brake fluid storage tank;

An electronic control unit, the electronic control unit is connected to the liquid level sensor to obtain liquid level detection data, characterized in that the electronic control unit has:

A first module, the first module generates an instruction to stop the motor vehicle in a horizontal or substantially horizontal posture;

a second module that generates instructions to determine the current fluid level in the brake fluid storage tank;

A third module, the third module generates an instruction to determine the volume change of the brake fluid in the brake fluid storage tank based on the previously determined reference fluid level and the current fluid level; and

The fourth module, when the wear thickness of the friction lining equipped for the front wheel or the rear wheel is known, the fourth module generates the volume change of the brake fluid in the brake fluid storage tank, the hydraulic pressure The diameter of the brake piston of the brake drive unit is used to determine the instruction of the wear thickness of the friction lining equipped for the rear wheel or front wheel accordingly.

Optionally, the fourth module stores the following formula to determine the wear thickness of the friction lining equipped for the rear wheel or the front wheel accordingly,

ΔL _X ＝(ΔV _L -πD ₀ ² ·ΔL ₀ -γ)/(πD _X ² ), where ΔL _X is the wear thickness of the friction lining to be determined, D ₀ is the friction lining corresponding to the known wear thickness The diameter of the brake piston of the brake device, D _X is the diameter of the brake piston of the brake device corresponding to the friction plate to be determined, ΔV _L is the change in the volume of the brake fluid in the brake fluid storage tank Quantity, γ is a non-zero empirical constant.

Optionally, the reference liquid level is the liquid level in the brake fluid storage tank when the thickness of the new friction plates of the same motor vehicle or all the friction plates of the same motor vehicle is known and the vehicle is stopped in a horizontal or substantially horizontal posture. bit.

Optionally, the premise that the fourth module generates the instruction is that no additional brake fluid is added to the brake fluid storage tank.

Optionally, a resistive sensor is arranged in the friction plate with known wear thickness to determine the wear thickness of the friction plate.

Optionally, an electronic parking brake (700) or an electromechanical brake (710) is configured for the friction lining with known wear thickness, so as to determine the wear thickness of the friction lining.

Optionally, the electronic parking brake or the electromechanical brake includes a driving motor and a piston driving member that is driven by the driving motor and can move linearly, and the braking piston is suitable for being driven by the piston when the motor vehicle is braking. The component is driven to contact the friction plate, thereby driving the friction plate to move.

Optionally, the electronic control unit also includes:

A fifth module, the fifth module generates an instruction to operate the driving motor to move the piston driving member to a predetermined reference position after the motor vehicle has been parked;

A sixth module which, after the fifth module, generates an instruction to operate the drive motor again to move the piston driver from the reference position to its rest position in contact with the brake piston , wherein the stop position corresponds to a parking brake position of the brake piston;

A seventh module, the seventh module generates a method for determining the distance between the reference position and the stop position, and compares the determined distance with the previously determined reference distance to determine the wear thickness of the tested friction plate as Instructions for the known wear thickness.

Optionally, the reference distance is determined when the thickness of the tested friction lining is known or the tested friction lining is a brand new friction lining and when the parking brake is performed. The distance to move to the stop position.

Optionally, the known wear thickness of the tested friction plate is the absolute value of the difference between the determined distance and the reference distance.

Optionally, the electronic control unit further includes an eighth module, the eighth module prompts the driver of the motor vehicle to replace the tested friction plate after the wear thickness of any one of the tested friction plates is lower than a predetermined value. instructions.

Optionally, the electronic parking brake or the electronic mechanical brake further includes a deceleration mechanism connected to the output shaft of the driving motor, and a linear movement mechanism driven by the deceleration mechanism, and the deceleration mechanism can provide It has a locking function to prevent the piston driving part from moving freely, and the piston driving part can move linearly by being driven by the linear moving mechanism through the driving motor.

Optionally, the linear movement mechanism is a threaded screw structure, the threaded screw structure includes a mandrel connected to the output shaft of the reduction mechanism, and the outer surface of the mandrel is formed with external threads, the The piston driving member is a threaded member, has an internal thread engageable with the external thread, does not rotate when the mandrel rotates, and can linearly move back and forth along the axial direction of the mandrel.

Optionally, the moving direction of the piston driving member to the reference position is opposite to the moving direction of the piston driving member from the reference position to the stop position.

By adopting the above-mentioned technical means of the present application, the loss of the friction lining can be continuously determined without any additional equipment for the friction lining, which provides a favorable basis for the user of the motor vehicle to replace the friction lining, and reduces the braking force. Design, manufacture, and assembly costs of the device. At the same time, by adopting the above-mentioned technical means of the present application, it is not necessary to equip the friction plates of each wheel of the motor vehicle with additional sensors or only to equip the friction plates of single-axle wheels with additional sensors, thereby reducing the overall vehicle design. , Assembly costs. In addition, the system and method of the present application can be implemented alone or alternatively as an advantageous supplement to the prior art in which additional sensors are provided to monitor friction lining wear.

Description of drawings

The principles and various aspects of the application will be more fully understood from the following detailed description in conjunction with the following drawings. It should be pointed out that the proportions of the drawings may be different for the purpose of clarity, but this will not affect the understanding of the present application. In the attached picture:

Figure 1 schematically shows an embodiment of a motor vehicle braking system suitable for use with the system and method for brake pad wear monitoring of the present application, wherein the motor vehicle braking system includes hydraulic brake actuation and an electronic parking brake capable of acting on only the two rear wheels and which is operable independently of the hydraulic brake actuation;

FIG. 2A schematically shows an example of an electronic parking brake (EPB), which is mounted relative to a brake caliper of a motor vehicle, and whose mechanism for driving a brake piston is The driving element is in its contact position with the brake piston, and it can even be in the stop position where the brake piston drives the friction plate to contact the brake disc for parking braking;

Fig. 2B schematically shows the same electric parking brake of Fig. 2A, wherein the drive element of the electric parking brake is in the start-to-stop position of the free travel before contacting the brake piston, ie the reference position;

Fig. 3 schematically shows the curve of the current of the driving motor of the electronic parking brake changing with time during operation;

Fig. 4A schematically shows a brake disc and friction linings acting on opposite sides thereof, wherein the motor vehicle is not in a parking brake state;

Fig. 4B schematically shows the same brake disc as shown in Fig. 4A and the friction linings acting on its opposite sides, wherein the motor vehicle is in the state of parking brake;

Fig. 5 schematically shows a flow chart of an embodiment of a method for monitoring wear of brake pads according to the present application;

Fig. 6 schematically shows a block diagram of an embodiment of a brake pad wear monitoring system according to the present application;

Fig. 7A schematically shows the situation of relying on the hydraulic brake driving device to drive the brake piston for parking braking, wherein the corresponding friction plate is a new friction plate;

Fig. 7B schematically shows the situation of relying on the hydraulic brake driving device to drive the brake piston for parking braking, wherein the corresponding friction plate is an old friction plate, such as the friction plate after the motor vehicle has traveled a certain mileage;

Fig. 8 schematically shows a flow chart of a method for monitoring brake pad wear according to another embodiment of the present application;

Fig. 9 schematically shows a block diagram of a brake pad wear monitoring system according to another embodiment of the present application.

Detailed ways

In the various figures of the application, structurally identical or functionally similar features are indicated by the same reference numerals.

Figure 1 schematically shows an embodiment of a motor vehicle braking system comprising a hydraulic brake actuator capable of acting on each wheel and an electronic brake actuator capable of acting on only the two rear wheels. a parking brake (EPB), and the electronic parking brake is operable independently of the hydraulic brake actuation. It should be clear to those skilled in the art that the electronic parking brake as shown in Figure 1 could alternatively act on only the two front wheels. Fig. 1 illustrates the principle of the present application by taking the electronic parking brake acting on two rear wheels as an example in a schematic but non-limiting manner. In the context of this application, motor vehicles include, but are not limited to, fuel motor vehicles, pure electric vehicles, hybrid vehicles, and the like.

As shown, the motor vehicle includes an electronic control unit (ECU) 100 for receiving signals from corresponding components and sending control signals to corresponding components; and a brake pedal 200, for example, the brake pedal 200 may be located in the cabin so that the driver can step on it as needed. For example, a motor vehicle includes four wheels, namely, a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. Each of the left front wheel FL, right front wheel FR, left rear wheel RL, and right rear wheel RR is equipped with a braking device, for example, the braking device of the left front wheel FL includes a The installed brake disc 500FL and two friction plates 610FL and 620FL which are located on opposite sides of the brake disc 500FL and are non-rotatably mounted with respect to the brake disc 500FL, for example, the two friction plates 610FL and 620FL It may be mounted on a brake caliper (not shown in FIG. 1 ) at least partially radially surrounding the brake disc 500FL. When the vehicle is not braking, the friction plates 610FL and 620FL are spaced apart from the brake disc 500FL, respectively. The friction plate 620FL is located on the side of the brake disc 500FL facing the left front wheel FL, and the friction plate 610FL is located on the side of the brake disc 500FL facing away from the left front wheel FL. When the motor vehicle needs to be braked, the friction plates 610FL and 620FL can be driven to move and clamp respectively towards the brake disc 500FL, thereby contacting the brake disc 500FL which rotates with the left front wheel FL, due to the friction generated by the contact, increasing The drag experienced by a motor vehicle to help it stop moving. The brakes of the right front wheel FR, left rear wheel RL and right rear wheel RR are similar to those of the left front wheel FL, including brake discs 500FR, 500RL, 500RR and Two friction plates 610FR and 620FR, 610RL and 620RL, 610RR and 620RR are located on opposite sides of the respective brake disc 500FR, 500RL, 500RR and are non-rotatably mounted relative thereto.

The hydraulic brake drive of the motor vehicle brake system includes a main brake pump 300 . The master brake pump 300 is operatively connected to the brake pedal 200 . Meanwhile, the master cylinder 300 is connected to the cylinder cylinders 310FL, 310FR, 310RL, and 310RR provided for each of the wheels FL, FR, RL, and RR via hydraulic lines. In addition, the brake fluid storage tank 400 can also communicate with these pumps via hydraulic lines. Each brake cylinder may include a cylinder and a brake piston, so that the brake piston can move linearly relative to the cylinder under the action of hydraulic pressure. Each brake cylinder 310FL, 310FR, 310RL and 310RR is installed at a corresponding brake caliper so as to be able to drive a corresponding pair of friction plates to move linearly toward a corresponding brake disc. In this way, when the brake pedal 200 is pressed, the brake main pump 300 drives the brake fluid through the hydraulic pipeline to act on the brake cylinders 310FL, 310FR, 310RL and 310RR, so that the corresponding friction plates and the corresponding brake Disc contact, causing the motor vehicle to stop moving. Under the control of the electronic control circuit 100, the brake cylinders of the front wheels FL, FR or the rear wheels RL, RR can be independently controlled and operated.

As further shown in FIG. 1 , for the left rear wheel RL and the right rear wheel RR, an electronic parking brake 700RL, 700RR is respectively equipped. Each electronic parking brake 700RL, 700RR is electrically connected to and controlled by the electronic control unit 100 . At the same time, each electronic parking brake 700RL, 700RR is installed on a corresponding brake caliper to act on a corresponding friction plate, and can operate independently from the corresponding brake cylinder 310RL, 310RR, so that, for example, when the motor vehicle has stopped In this case, the corresponding friction plates of the left rear wheel RL and/or right rear wheel RR move toward and contact their brake discs, thereby relying on the friction between the friction plates and the brake discs to ensure the parking brake of the motor vehicle.

For example, FIG. 2A schematically shows an electronic parking brake, which may be the electronic parking brake 700RL or 700RR shown in FIG. 1 . It should be pointed out that all the drawings in this application are only given to illustrate the principle of this application, and it cannot be considered that the specific component design must complete the installation of the structure shown in the drawings.

The electronic parking brake is mounted relative to a brake caliper 630 which may be mounted at least partially surrounding the brake disc 500RL or 500RR. The brake caliper 630 is fixedly mounted relative to the vehicle body or relative to the suspension. The electronic parking brake includes a drive motor 311 fixedly mounted relative to a brake caliper 630 . Meanwhile, the electric parking brake also includes a spindle 316 rotatably mounted relative to the brake caliper 630 . In addition, the outer surface of the core shaft 316 is sheathed with a threaded member 317 that cannot rotate and can only reciprocate linearly along the axial direction. The outer surface of the mandrel 316 is formed with external threads, and the central hole of the screw member 317 is formed with internal threads so that the external threads and the internal threads can engage with each other. Furthermore, the threaded member 317 can be located within the hollow chamber of the brake piston 319 or move independently relative to the brake piston 319 . At the same time, the brake piston 319 is guided linearly displaceably in the cylinder 320 . The cylinder block 320 is fixed relative to the brake caliper 630. It should be clear to those skilled in the art that the brake piston 319 and the cylinder body 320 may constitute the same brake piston and cylinder body of the aforementioned corresponding brake cylinder. In fact, the piston driving force generated by the electronic parking brake and the piston driving force generated by the brake main cylinder 300 via the corresponding brake cylinder can be able to act on the brake piston 319 independently of each other. The interaction of the electric parking brake with the brake piston 319 can be decoupled if required. In the context of this application, the term "decoupled" means that two associated elements or devices do not exert a driving force on each other.

The threaded part 317 can be guided linearly with its outer surface non-rotating, or in the hollow chamber of the brake piston 319 with its outer surface non-rotating, so that the threaded part 317 and the mandrel 316 form a A threaded screw structure or a threaded screw structure is formed between the screw 317 and the mandrel 316, so that the screw 317 that does not rotate with the mandrel 316 can rely on the thread engagement between the two to move along The axis of the mandrel 316 moves linearly back and forth. Thus, for example during parking braking, the linear movement of the threaded member 317 can ensure that it contacts the brake piston 319 and thus drives the brake piston 319 against the corresponding friction plate, thereby ordering the opposite arrangement with the help of the brake caliper 630 The two friction plates of the two friction plates contact the corresponding brake disc at the same time, and then apply pressure to the friction plate to generate the required parking friction braking force on the brake disc, that is, the brake piston 319 is in its parking brake position at this time .

Of course, due to the characteristics of the threaded screw structure, along with the reverse rotation of the mandrel 316, the threaded part 317 that has been in contact with the brake piston 319 in the parking brake position can move linearly in the opposite direction, so that the threaded part 317 no longer The brake piston 319 applies force. This means that the electric parking brake is decoupled from brake piston 319 . Certainly, when decoupling, the distance of the reverse linear movement of the threaded member 317 may depend on the time of the reverse rotation of the mandrel 316 or even the design of the mechanical limit of the threaded screw structure itself. Under normal circumstances, in order to release the parking brake, it is only necessary to reversely rotate the mandrel 316 to the extent that the threaded member 317 is just out of contact with the brake piston 319, so as to ensure that the parking brake force is no longer controlled by the friction plate. applied to the brake disc. At the same time, it is also convenient for the hydraulic brake driving device to quickly drive the brake piston in response to the braking demand during the subsequent driving process, so that the friction plate contacts the brake disc again to apply the driving braking force. In the above examples of the present application, the threaded screw structure forms a linear movement mechanism, which can be driven by the reduction mechanism described below, so as to drive the screw 317 to move linearly. Of course, those skilled in the art should be aware that any other suitable mechanism capable of converting rotational motion into linear motion can be used as the linear movement mechanism in the technical solution of the present application.

Turning to FIG. 2A , the electric parking brake includes a reduction mechanism 315 mounted relative to a brake caliper 630 . The input end of the reduction mechanism 315 is connected with the output shaft of the drive motor 311, and the output end of the reduction mechanism 315 is connected with the mandrel 316, so that the positive and negative rotation of the output shaft of the drive motor 311 can be driven by the output of the reduction mechanism 315 The mandrel 316 rotates forward and backward. As just one example, the reduction mechanism may be a double-stage worm gear reduction mechanism installed on the brake caliper 630, including a first reduction stage composed of a first-stage worm and a first-stage turbine engaged with each other, and a second-stage worm engaged with each other. The second deceleration stage is composed of a secondary worm, wherein the primary worm is connected to the output shaft of the drive motor 311, the secondary worm is connected to the core shaft 316, and the primary worm and the secondary worm are formed on the same rotating shaft. The deceleration mechanism constituted in this way can ensure that the locking effect is provided when the parking brake is performed, that is, the brake piston 317 will not be transmitted to the drive motor through the screw 317, the spindle 316 and the deceleration mechanism through the reaction force caused by the friction plate. The output shaft of the 311 causes it to rotate accordingly. Of course, those skilled in the art should be clear that other forms of reduction mechanisms that can provide a parking brake locking effect, such as a single-stage worm gear reduction mechanism or even a reduction gear mechanism with a locking function, etc., can also be used in this application. adopted in the technical scheme.

The threaded part 317 can also be referred to as the piston driving part 317 of the electronic parking brake. Therefore, it can be seen that during parking braking, if the pitch of the threaded screw structure, the reduction ratio of the reduction mechanism 315, and the running time of the output shaft of the drive motor 311 are known, the relationship between the piston driver 317 and the The distance between the position where the brake piston 319 disengages and the position where it pushes the brake piston 319 (for example, this position corresponds to the parking brake position of the brake piston 319 ).

FIG. 3 schematically shows the current curve measured and obtained when the driving motor 311 of the electronic parking brake is in operation. During the operation of the electronic parking brake, the operating current of the driving motor 311 can be detected through a corresponding detection circuit and the detection result can be sent to the electronic control unit 100 . When parking braking is required, the drive motor 311 is energized and started. Due to the characteristics of the motor itself, a large starting current is usually generated, which is shown as a current peak A in the current curve of Figure 3. After passing through the current peak value A, the operating current drops rapidly, and along with the drive motor 311 drives the piston driver 317 through a speed reduction mechanism and threaded screw structure to experience a section of free travel (during this period, the piston driver 317 has not yet contacted the brake piston 319 contact), the operating current of the driving motor 311 is stable, that is, corresponding to the curve from t _A to t _C. Then, at time t _C , the piston driver 317 comes into contact with the brake piston 319 and further causes the brake piston 319 to drive the corresponding friction plate to move towards the brake disc and to contact it. During this period, the operating current of the driving motor 311 rises rapidly because the piston driving member 317 experiences corresponding resistance from the brake piston 319 . Finally, when the brake piston 319 reaches its parking brake position, in order to ensure that the drive motor 311 is damaged due to excessive operating current, a corresponding cut-off current peak value B (at time t _B ) will be set for the drive motor 311 . When the working current reaches the peak value B of the cut-off current, the driving motor 311 will be forced to stop. At this time, at time t _B , due to the locking effect of the above-mentioned deceleration mechanism, the brake piston 319 is held at the parking braking position via the piston driver 317 and the deceleration mechanism, and the electronic parking brake completes the parking brake. . When driving is required, the drive motor 311 is started again so that its output shaft rotates in reverse, to ensure that the piston driver 317 moves in a reverse straight line to the extent that the brake piston 319 is not just in its parking brake position, so that the corresponding friction plates There is no parking braking force generated by the electronic parking brake between the brake disc and the brake disc, that is, the electronic parking brake is decoupled from the brake piston 319 .

Therefore, it can be seen that during the parking brake of the motor vehicle in the prior art, along with the continuous wear and tear of the friction lining, the initial position of the piston driving member 317 when performing the parking brake is almost randomly determined. In order to ensure that the specific linear movement distance of the piston driving member 317 during parking braking can be identified with a unified evaluation standard, the initial position of the piston driving member 317 can be artificially set. Usually, in the threaded screw structure design between the piston driving part 317 and the mandrel 311, a stop feature such as a stopper will be provided at a certain position in the axial direction of the mandrel 311, thereby limiting the piston driving part 317 along the The direction away from the brake piston 319 can move to the maximum extent, as shown in FIG. 2B . For a manufactured electronic parking brake, the limit of the piston driving member 317 corresponding to the maximum movement degree is always fixed, so it can be regarded as a reference position of the piston driving member 317 . That is, if the piston driver 317 is deliberately first moved to a reference position each time the parking brake is applied, then the measurement is from when the piston driver 317 begins to move until finally the brake piston 319 reaches its parking brake position time, the distance from the reference position to the stop position (corresponding to the parking brake position) of the piston driving member 317 can be measured.

Those skilled in the art should be aware that the above starting current peak time t _A , steady-state transition time t _C , and cut-off current peak time t _B can be detected by relevant electronic circuits and transmitted to the electronic control unit 100 for recording. Therefore, through the program setting in the electronic control unit 100, the current curve can be recorded every time the parking brake is performed, and then by detecting a predetermined detection time period, and then using the detection time period according to the following formula 1 Determine the moving distance L of the friction pads from the initial position to the position where the parking brake is applied.

L=f1(Δt _E ,η,p) Formula 1

Wherein, L is the moving distance of a single friction plate, Δt _E is the time for the piston driver 317 of the electronic parking brake to move from its reference position to its stop position (corresponding to the parking brake position of the brake piston 319), η is the transmission ratio of the reduction mechanism, p is the pitch of the threaded screw structure 317, and f1 can be a function associated with Δt _E , η, p. Certainly, those skilled in the art should understand that although Δt _E is |t _A −t _B | in the examples described below, this is only for the convenience of estimation. In an alternative example, Δt _E can also be chosen as |t _A −t _C |. That is to say, it can be artificially set whether the transition current point C or the cut-off peak point B corresponds to the parking brake position where the brake piston 319 is located.

For example, as an example, f1=(n _M /η)·p·Δt _E /2, where n _M is the rotational speed of the driving motor 311 . As another example, it is also possible to consider adding a correction factor related to other factors in the f1 function, such as adding a correction factor related to the thickness wear of the brake disc (the correction factor can be determined based on a large number of experiments in advance), so that f1= (n _M /η)·p·Δt _E /2+θ, where θ is a correction coefficient, for example, a correction coefficient related to the thickness wear of the brake disc.

Assume that the transition current point C and the cut-off peak point B are the corresponding points on the operating current curve of the drive motor 311 corresponding to the new friction plate, and the transition current point C' and the cut-off peak point B' are the same as the friction plate has been working. Corresponding points on the operating current curve of the drive motor 311 under corresponding circumstances after a certain period of time. In this way, as shown in Figures 4A and 4B (for clarity, Figures 4A and 4B exaggerate the gap between the friction lining and the brake disc when they are not in contact), after the new friction lining has been installed in place, use The above formula 1 records the time of the piston driver 317 from the reference position to the stop position during parking braking by activating the electronic parking brake, Δt _E = |t _A -t _B |, and then calculates the piston according to the above formula 1 The moving distance L _O of the driving member 317 is the reference distance. Then, apply the parking brake after the friction linings have worn out for a period of time. If it is necessary to evaluate the thickness of the friction plate at this time, when performing parking braking, first activate the electronic parking brake, so that its piston driving member 317 moves to the reference position, and then reversely activate the driving motor 311 of the electronic parking brake , so that the distance L _A for the piston driver 317 to move from its reference position to the stop position corresponds to the time Δt _E = |t _A −t _B′ |. Since the piston driver 317 returns to its reference position whenever the parking brake is performed and needs to be measured, and then counts from the reference position to the stop position, so when the performance of the driving motor 311 remains unchanged, the same as The starting current moment t A corresponding to the starting current point _A is always constant, thereby ensuring the comparison calculation basis between each calculated _LA and the initially calculated _LO . That is to say, ΔL _R =|L _{O -LA} | is the thickness loss of the friction plate. In the context of the present application, the first determined distance corresponding to a new friction plate or the average value of the first few determined distances can be regarded as the reference distance L _O of the piston driving member 317 .

The ingenuity of the method for determining the thickness loss of the friction lining in this application is that although the time period |t _B -t _C | corresponding to the parking brake of the new friction lining is necessarily smaller than that of the friction lining after a certain period of time The time period corresponding to the parking brake |t _B' -t _C' |, but the difference between the two will be very small, requiring very high confirmation accuracy of point C and the relatively small time difference will inevitably lead to a relatively small large calculation error. The present application first returns the piston driving member 317 to its reference position each time, so that the movement of the piston driving member 317 can be estimated by using the starting current time t _A of the driving motor 311 to the cut-off peak time t _B or t _B′ with a unified standard distance. Since the time difference from the starting current moment t _A to the cut-off peak moment _tB or _tB' is significantly greater than the time difference from the transition current moment _tC or _tC' to the cut-off peak moment _tB or _tB' , the possibility of calculation errors is reduced To ensure the accuracy of the final calculation.

Therefore, for a motor vehicle equipped with an electronic parking brake, the present application provides an ingenious monitoring method suitable for continuously monitoring the wear thickness of the friction lining used in conjunction with the electronic parking brake.

Fig. 5 schematically shows a flow chart of an embodiment of a method for monitoring wear of brake pads according to the present application. It should be clear to those skilled in the art that the method or each method step introduced in this application can be coded and stored in the memory of the electronic control unit 100 as a program and invoked and executed by it. In step S10, it is determined whether the motor vehicle has come to a complete stop. For example, the basis for judging whether the motor vehicle has stopped safely may be based on summarizing various existing sensors in the motor vehicle. On the premise that the judgment in step S10 is "Yes", go to step S14; otherwise, stop the monitoring of the wear of the brake friction lining this time. In step S14, for the consideration of parking brake safety, the brake cylinders of the wheels not equipped with electronic parking brakes are first activated, so as to ensure that the wheels not equipped with electronic parking brakes are in a braking state. Next, at step S15, the electric parking brake is activated so that its driving motor 311 operates in a manner that ensures that the piston driving member 317 returns to its reference position, and finally ensures that the piston driving member 317 is in its reference position. Then in step S20, activate the electronic parking brake 700RL, 700RR as shown in FIG. The gear ratio η of the mechanism and the pitch p of the threaded screw structure are used to determine the loss of each friction plate of the rear wheels RL and RR equipped with electronic parking brakes 700RL and 700RR when using the parking brake. The moving distance difference ΔL _R during monitoring, for example, the Δt of the drive motor 311 can be based on the Δt _E used to determine L _O or _LA in FIG. 4A and FIG. 4B .

Then, in step S30, it is first judged whether the parking brake measurement is performed for the first time; if the judgment result is "yes", it means that the calculation result of step S20 is L _O , and now the calculation result is recorded as the reference distance L _O for future use. For example, this process can be executed when the vehicle of the OEM is off the assembly line or new friction linings are replaced at the 4S shop; if the judgment result is "No", it means that the calculation result of step S20 is L _A The absolute value ΔL of the difference between the moving distance L _A of the wear monitoring of the friction lining and the reference distance L _O recorded for the first time is used to determine the thickness loss value of the current friction lining.

Next, in step S60, if the obtained thickness loss value of the current friction plate is greater than or equal to a predetermined value, then go to step S70. For example, in step S70, the indicator in the cockpit can be activated to issue visual and/or sound alarms to the driver, and/or some functions of the motor vehicle can be restricted, such as the speed at which the motor vehicle travels. Carry out restrictions, such as a maximum speed limit of 50 km/h, thereby arousing the driver's vigilance. If the current thickness loss value of the friction plate obtained in step S60 is less than the predetermined value, then go to step S80, and send the test data to the instrument panel or the driver's mobile electronic device for display as regular status prompt information. In step S80, continue to perform parking braking according to the electronic parking brake to ensure safe parking of the motor vehicle, and at the same time selectively release brake cylinders of wheels not equipped with electronic parking brakes.

In the above-mentioned embodiment, although the basic ideas of the present application have been introduced with the electronic parking brakes 700RL and 700RR equipped on the rear wheels RL and RR, those skilled in the art should understand that for only the front wheels FL and FR are equipped with electronic parking brakes. For motor vehicles with brakes, the basic idea of the application is equally applicable.

In an alternative embodiment, the idea of the present application is also applicable to motor vehicles equipped with electromechanical brakes (EMB). In the context of this application, an electromechanical brake refers to a device capable of driving a brake piston to generate a frictional braking force between a friction plate and a brake disc, whether in service braking or parking braking. Of course, such electromechanical brakes can act on each of the four wheels of the motor vehicle. At the same time, motor vehicles equipped with such electromechanical brakes can retain the hydraulic brake actuation as a brake safety barrier protection, or even hydraulic brake actuation, and only rely on the electromechanical brake for service and parking braking. It should be clear to those skilled in the art that this hydraulic brake driving device generally also includes a driving motor, a reduction mechanism operatively connected with the driving motor and having a locking function during braking, and a piston driving mechanism operatively connected with the reduction mechanism. parts, so that it can act on the brake piston and drive the corresponding friction plate to move.

Therefore, the method described above also applies to motor vehicles equipped with electromechanical brakes. For example, for a motor vehicle equipped with only electro-mechanical brakes, step S10 shown in Figure 5 above can be changed to use the electro-mechanical brakes to park and brake the two front wheels first, and use the electronic The mechanical brakes determine the degree of pad wear on the rear wheels, and then use the electro-mechanical brakes on the rear wheels for parking braking, while the operation of the electro-mechanical brakes on the front wheels determines the degree of pad wear on the front wheels.

Based on what has been described above, it can be considered that the present application proposes a method for monitoring the loss of brake pads of a motor vehicle, wherein the motor vehicle includes brakes acting on each of the two front wheels or the two rear wheels. The braking device has a brake disc mounted rotatably with the wheel, a friction plate that is non-rotatable relative to the wheel but can move linearly parallel to the axis of rotation of the wheel, a cylinder block fixedly mounted relative to the vehicle body, and a brake piston movable linearly in said cylinder, said motor vehicle also includes an electronic parking brake or an electromechanical brake respectively equipped on each of the two front wheels or the two rear wheels, said electronic The parking brake or the electro-mechanical brake includes a drive motor, a reduction mechanism connected to the output shaft of the drive motor, a linear movement mechanism driven by the reduction mechanism, and a piston driver capable of linear movement driven by the linear movement mechanism , the deceleration mechanism can provide a locking function that prevents the piston driver from moving freely during braking, and the brake piston is adapted to be driven by the piston driver to contact the friction plate, thereby driving the friction pieces move,

The methods include:

operating the driving motor to move the piston driving member to a predetermined reference position after the motor vehicle has been parked;

Operating the drive motor again to move the piston driver from the reference position to its stop position in contact with the brake piston, wherein the stop position corresponds to the parking brake of the brake piston location correspondence;

determining a distance between the reference position and the stop position;

The determined distance is compared with the previously determined reference distance to determine the wear thickness of the tested friction plate.

In addition, it can also be considered that the present application proposes a motor vehicle brake friction lining wear monitoring system. The motor vehicle comprises a braking device acting on each wheel having a brake disc mounted rotatably with the wheel and a friction disc which is non-rotatable with respect to the wheel but movable linearly parallel to the axis of rotation of the wheel piece. Said motor vehicle comprises a braking device acting on each of the two front wheels or the two rear wheels, said braking device having a brake disc mounted rotatably with the wheel, non-rotatable relative to the wheel but Friction linings that can move linearly parallel to the axis of rotation of the wheel, a cylinder fixedly mounted relative to the body, and a brake piston that can move linearly in said cylinder.

As further shown in Figure 6, the system includes:

An electronic parking brake 700 or an electromechanical brake 710 correspondingly equipped with each of the two front wheels or the two rear wheels, the electronic parking brake or the electromechanical brake includes a drive motor, and an output of the drive motor A deceleration mechanism connected to the shaft, a linear movement mechanism driven by the deceleration mechanism, and a piston driver capable of linear movement driven by the linear movement mechanism, and the deceleration mechanism can prevent the piston driver from randomly moving when braking. a mobile locking function, the brake piston being adapted to be driven by the piston drive member into contact with the friction lining, thereby driving the friction lining to move; and

An electronic control unit 100 , the electronic control unit 100 is electrically connected to the electronic parking brake 700 or the electromechanical brake 710 to control the operation of the electronic parking brake 700 or the electromechanical brake 710 . The electronic control unit 100 includes: a first module 1001, the first module 1001 generates an instruction to operate the driving motor to move the piston driving member to a predetermined reference position after the motor vehicle is parked ;

The second module 1002, the second module 1002 generates an instruction to operate the drive motor again to move the piston drive member from the reference position to its stop position in contact with the brake piston, wherein the The stop position corresponds to the parking brake position of the brake piston;

A third module 1003, the third module 1003 generates an instruction to determine the distance between the reference position and the stop position; and

A fourth module 1004, the fourth module 1004 generates an instruction for comparing the determined distance with a predetermined reference distance to determine the wear thickness of the tested friction lining.

The reference distance is determined when the thickness of the tested friction plate is known or the tested friction plate is brand new and the piston driving member moves from the reference position to the The distance to the stop position. It should be pointed out that although the reference distance needs to be determined when the tested friction plate is a brand-new friction plate in the illustrated embodiment, those skilled in the art should know that the determination of the reference distance requires the thickness of the tested friction plate to be allow. That is to say, when the thickness of the friction plate to be tested is known, the reference distance can be determined in advance. Of course, when the tested friction lining is a brand new friction lining, the thickness of the brand new friction lining is of course known. If the tested friction plate is a used friction plate, it is only necessary to measure and record the thickness of the tested friction plate, and then determine the reference distance accordingly to apply the method or system of the present application.

The wear thickness of the tested friction plate is the absolute value of the difference between the determined distance and the reference distance.

Each wheel of the motor vehicle is equipped with only the electromechanical brake.

The electronic control unit 100 also includes a fifth module 1005 for generating an instruction to remind the driver of the motor vehicle to replace the tested friction plate after the wear thickness of the tested friction plate is lower than a predetermined value. For example, the electronic control unit 100 may be connected with a buzzer alarm, so that the buzzer alarm sends out a buzzer alarm after receiving the instruction generated by the fifth module 1005 . For example, for a motor vehicle with only front or rear wheels equipped with electronic parking brakes, the predetermined value may be determined according to the manufacturer's long-term friction lining replacement monitoring habits for motor vehicle users.

The linear movement mechanism is a threaded screw structure, the threaded screw structure includes a mandrel connected to the output shaft of the reduction mechanism, and the outer surface of the mandrel is formed with external threads, and the piston driver is The threaded member has an internal thread engageable with the external thread and does not rotate when the mandrel rotates so as to be able to linearly move back and forth along the axial direction of the mandrel.

The distance between the reference position and the stop position depends at least on the rotation speed of the driving motor, the transmission ratio of the reduction mechanism, the lead screw pitch of the threaded screw structure and the power-on time of the driving motor.

Where the motor vehicle is equipped with an electronic parking brake, the motor vehicle also includes applying the hydraulic brake actuation means to apply parking brakes to wheels not equipped with the electronic parking brake prior to performing the wear thickness determination Hydraulic brake drive unit. The electronic control unit comprises a seventh module 1007 controlling the hydraulic brake drive.

The electronic control unit 100 also includes a sixth module 1006, the sixth module 1006 generates an instruction to determine the current thickness according to the wear thickness of the tested friction lining and/or generates a display of the current thickness of the tested friction lining commands on the dashboard of a motor vehicle or sent to the driver's mobile electronic device. For example, the instruction can be sent to the dedicated display instrument on the dashboard of the motor vehicle via the existing bus of the motor vehicle, or can also be sent to the driver's mobile phone, laptop computer and other mobile electronic devices via WiFi, mobile network, etc.

The current thickness of the tested friction plate is equal to the thickness of a new friction plate of the same specification minus the worn thickness of the tested friction plate.

The direction of movement of the piston driver to the reference position is opposite to the direction of movement of the piston driver from the reference position to the stop position.

The electronic control unit 100 also includes an eighth module 1008. In the case that all the front and rear wheels of the motor vehicle are equipped with electromechanical brakes, the eighth module 1008 generates an electromechanical brake on the front wheels to parking brake, and then use the electro-mechanical brake of the rear wheel to determine the wear thickness of the friction lining of the rear wheel; or, generate a command to first apply the parking brake to the rear wheel Electromechanical brakes determine the command of the wear thickness of the friction linings of the front wheels.

In order to determine the wear condition of friction linings of wheels not equipped with electronic parking brakes or electromechanical brakes, the system and method for monitoring brake friction lining wear of a motor vehicle according to other embodiments of the present application are introduced below.

Fig. 7A schematically shows the situation of relying on the hydraulic brake driving device to drive the brake piston for parking braking, where reference numeral 500 represents a brake disc, for example, the brake disc 500FL shown in Fig. 1 , 500FR, 500RL, 500RR; reference numerals 610, 620 represent friction plates, such as friction plates 610FL, 620FL; 610FR, 620FR; 610RL, 620RL; 610RR, 620RR shown in FIG. 1 . In addition, reference numeral 320 denotes a cylinder of a brake cylinder, and reference numeral 319 denotes a brake piston of a brake cylinder. It should be clear to those skilled in the art that the cylinder body 320 and the brake piston 319 may be the cylinder body and the brake piston of the brake wheel cylinder corresponding to the wheels not equipped with electronic parking brakes or electromechanical brakes, or they may be as shown in the figure 2A and 2B have already described the cylinder and brake piston in the embodiment. The cylinder 320 is fixedly mounted relative to the brake disc 500, and when braking is required, the brake piston 319 can move towards the friction plate 610 under the action of pressurized brake fluid, so that it is not shown in FIG. 7A Under the action of the extended brake calipers, the two friction plates 610, 620 can press and contact the brake disc 500 at the same time to provide frictional braking force thereto.

It should be pointed out that a sealing ring structure is usually provided between the brake piston 319 and the cylinder body 320 . In addition to ensuring that the brake fluid will not leak from the gap between the brake piston 319 and the cylinder body 320, this sealing ring structure also has an important function that the brake fluid is self-made whenever there is no need for braking. When the pressure of the moving piston 319 is released, the brake piston 319 can always retreat slightly away from the friction plate 610 driven by the sealing ring structure, so as to ensure that it is out of contact with the friction plate 610 . Usually, the degree of retreat is very small, it is difficult to observe with the naked eye, and it only depends on the elasticity of the sealing ring structure, so this retreat distance can be considered as a constant.

The volume enclosed by the brake piston 319 and the cylinder 320 is in fluid communication with the brake fluid storage tank 400 via corresponding hydraulic lines. Therefore, when the expansion of the hydraulic pipeline itself is ignored, due to the volume incompressibility of the brake fluid of the motor vehicle, the change in the volume space surrounded by the brake piston 319 and the cylinder body 320 will inevitably lead to braking. The liquid level of the brake fluid in the dynamic fluid storage tank 400 changes. As shown in FIG. 1 , the brake fluid storage tank 400 is usually equipped with a liquid level sensor 410 .

Now, it is assumed that the friction plates 610, 620 in Fig. 7A are new friction plates; piece. It can be seen that if only hydraulic braking is considered, since the volume space surrounded by the brake piston 319 and the cylinder body 320 is filled with brake fluid every time the brake fluid is pressurized, the brake piston 319 presses the friction plate 610, so even after the brake pressure is released The moving piston 319 will retreat in a constant slight amount (due to the above-mentioned sealing ring structure), but in the long run, the volume space surrounded by the brake piston 319 and the cylinder body 320 will inevitably increase due to the thinning of the friction plate 610 , for example represented by ΔV in the figure, which corresponds to the wear thickness ΔL of friction lining 610 and leads to a decrease in the fluid level in brake fluid reservoir 400 , which can usually be detected by fluid level sensor 410 . The liquid level sensor 410 may be electrically connected with the electronic control unit 100 so as to transmit detection data thereto.

Therefore, one of the main ideas of the present application is to use the liquid level sensor 410 to adjust the brake fluid storage tank 400 of the motor vehicle with the newly installed friction plate under the premise of not adding brake fluid or keeping the original brake fluid capacity unchanged. The brake fluid level in the vehicle is detected and recorded as the reference liquid level; then, after the motor vehicle travels for a certain mileage (such as 3, 5, 80,000 kilometers, etc.), the liquid level sensor 410 is used to detect the liquid level and the reference liquid level again. At the same time, consider the wear thickness of the friction lining that can be determined in advance to determine the wear thickness of other friction linings that have not been determined. For example, the above-mentioned reference liquid level may be the average value of multiple liquid level measurements within a specified period of time immediately after the new friction plate is installed, such as within one week, so as to eliminate errors caused by a single measurement as much as possible.

Still with the embodiment shown in FIG. 1, assuming that the wear thickness of the friction lining of the rear wheel has been determined by the method shown in FIG. 5, it is now necessary to further determine the wear thickness of the front wheel by using the method introduced with reference to FIGS. The wear thickness of the friction lining.

For example, in the case where the reference liquid level has been recorded, after the motor vehicle travels a certain mileage, the brake fluid occupancy volume corresponding to the reference liquid level and the actual liquid level detected by the liquid level sensor 410 correspond to the brake fluid level. The difference ΔV _L in the liquid occupied volume satisfies the following formula.

ΔV _L ＝f2(D _F ,ΔL _F ,D _R ,ΔL _R )

Among them, D _F represents the diameter of the brake piston of the brake cylinder acting on the front wheel, which can be measured in advance; ΔL _F represents the wear thickness _of the front wheel friction plate (that is, the single friction plate of the front wheel); The diameter of the brake piston of the wheel brake cylinder can be measured in advance; ΔL _R represents the wear thickness of the rear wheel friction plate (ie, the front wheel single-plate friction plate). f2 is a function that depends on D _F , ΔL _F , _DR , ΔL _R .

As an example (still using the embodiment shown in Fig. 2A and 2B as an example), the wear thickness ΔL _R of the single friction plate of the rear wheel has been determined by the method shown in Fig. 5 , so that the corresponding single rear wheel The volume of brake fluid that is additionally inhaled due to the wear thickness ΔL _R of the cylinder block of the brake cylinder installed on the brake caliper of the wheel during braking should be:

2·1/4·πD _R ² ·ΔL _R ,

Therefore, the volume of brake fluid additionally inhaled by the cylinder of the brake cylinder installed on the brake calipers corresponding to the two rear wheels due to the wear thickness ΔL _R during parking braking should be:

2·1/4·πD _R ² ·2ΔL _R .

It should be pointed out that here ΔL _R can be determined in advance by using the method shown in FIG. 5 .

Similarly, when the cylinders of the brake cylinders installed on the brake calipers of the two front wheels that are not determined by the method shown in Fig _. The volume of brake fluid additionally drawn in should be:

2·1/4·πD _F ² ·2ΔL _F .

It should be pointed out that ΔL _F is unknown here.

Considering the liquid volume incompressibility of the brake fluid, the brake fluid additionally inhaled by the above-mentioned front wheel and rear wheel brake cylinders due to the wear and tear of the corresponding friction plate thickness will inevitably cause the fluid in the brake fluid reservoir 400 to (That is to say, the brake fluid stored in the brake fluid reservoir 400 will inevitably reduce), and at the same time, a correction factor γ is added in consideration of factors such as brake disc wear and pipeline loss (it can be used in advance in the product depending on the extensive calibration tests performed during the development phase), then

The brake fluid volume change ΔV _L in the brake fluid reservoir 400 due to the above-mentioned front wheel and rear wheel brake cylinder cylinders being additionally sucked due to the wear and tear of the corresponding friction plate thickness:

ΔV _L ＝2·1/4·πD _F ² ·2ΔL _F +2·1/4·πD _R ² ·2ΔL _R +γ

＝πD _F ² ·ΔL _F +πD _R ² ΔL _R +γ

Therefore, in the case where ΔV _L can be determined by using the liquid level sensor 410 of the fluid dynamic accumulator 400, and D _F , _DR , and ΔL _R can all be determined,

The wear thickness ΔL _F of the single friction plate of the front wheel can be solved by the following formula 2, namely

ΔL _F ＝(ΔV _L -πD _R ² ·ΔL _R -γ)/(πD _F ² ) Formula 2

Of course, Formula 2 can also be modified as ΔL _x =(ΔV _L -πD ₀ ² ·ΔL ₀ -γ)/(πD _x ² ), where ΔV _L is the brake fluid storage tank 400 determined according to the liquid level sensor 410 ΔL ₀ is the known wear thickness of the single-plate friction plate, D ₀ is the diameter of the brake piston on the brake caliper corresponding to the known wear thickness of the single-plate friction plate (can be measured in advance Determined), γ is the correction system (can be determined in advance), D _x is the diameter of the brake piston on the brake caliper corresponding to the single friction plate with unknown wear thickness (can be determined in advance), ΔL _x is the The wear thickness of a single friction plate.

It should be clear to those skilled in the art that the above method ignores the impact on the change of the liquid level due to the brake piston retreating a constant distance after the brake is released by using the brake piston to drive the friction plate for braking in the case of hydraulic braking only. This is because the liquid level change is relatively uniform, and has the same impact on the old and new friction plates, and is very small, and usually does not cause the liquid level change in the brake fluid storage tank 400 .

It can be seen that the ingenuity of the above-mentioned brake pad loss monitoring of the present application is that only by comparing the liquid level measurement value of the brake fluid level sensor 410 after the motor vehicle travels a certain mileage with the reference liquid level, it can Calculate the wear thickness of the friction linings of wheels without electric parking brakes. Of course, those skilled in the art should be clear that, for a motor vehicle equipped with electromechanical brakes (for example, only equipped on the front wheels or rear wheels) and a hydraulic brake drive device, the use of the fluid level sensor 410 described here to estimate is not equipped with The method for the wear thickness of the wheel friction linings of electromechanical brakes is also applicable.

Of course, only taking Figure 1 as an example, in addition to using the electronic parking brake equipped on the rear wheels to determine the ΔL _R of the rear wheel friction plates, it is also possible to use a resistive sensor for the rear wheel friction plates to determine the corresponding rear wheel ΔL _R of the friction plate. For example, this resistive sensor known to those skilled in the art can be at least partially arranged in the friction lining of the rear wheel, such as the friction lining on one side of the brake disc, so that the resistance sensor can The sensor can output different resistance values. Furthermore, the resistive sensor can be electrically connected to the electronic control unit 100 so as to output resistance data to the latter. Of course, the resistance output of this resistive sensor is usually discontinuous, that is, only when the friction plate reaches the loss level calculated in advance, the changed resistance value will be output (for example, it can be a plurality of loss levels designed in advance corresponding to the changed resistance of multiple outputs). However, for a friction plate equipped with such a resistive sensor, through prior calculation, the changed resistance value of each output can correspond to the current thickness of the friction plate or in other words can correspond to the worn thickness of the friction plate . Furthermore, taking this resistive sensor installed on the corresponding friction plate of the rear wheel as an example, when the electronic control unit 100 obtains a changed resistance value output, it can infer the wear thickness of the friction plate accordingly. In this way, for example, the above-mentioned formula 2 can calculate the wear thickness of the friction plate of the wheel (such as the front wheel in FIG. 1 ) that is not equipped with an electronic parking brake.

Fig. 8 schematically shows a flow chart of a method for monitoring wear of brake pads according to another embodiment of the present application. It should be clear to those skilled in the art that the method or each method step introduced in this application can be coded and stored in the memory of the electronic control unit 100 as a program and invoked and executed by it.

First, in step S100, start the loss monitoring. For example, for motor vehicles with only front or rear wheels equipped with electronic parking brakes or electromechanical brakes and/or with only front or rear friction pads equipped with resistive sensors, the The method determines the wear thickness of the friction plate of the front wheel or the rear wheel or the resistive sensor has issued a resistance value change output value so that the wear thickness of the friction plate can be determined. Next, in step S110, it is determined whether the motor vehicle has stopped. For example, the basis for judging whether the motor vehicle has stopped in a horizontal or roughly horizontal posture may be based on summarizing information from various sensors that already exist in the motor vehicle. The purpose of doing this is to ensure that the current liquid level value can be recorded on a unified basis every time the liquid level sensor 410 of the brake fluid is used to detect the liquid level, so as to facilitate later comparative calculations. If the judging result of step S110 is that the motor vehicle is currently parked in a horizontal or substantially horizontal posture, go to step S140; otherwise, stop executing the method of the present application. In step S140, the liquid level sensor 410 can be used to determine the current liquid level of the brake fluid in the brake fluid storage tank 400, and the reference liquid level that has been determined when the friction plate is newly installed or the thickness of all friction plates of the same motor vehicle The already determined reference fluid level is compared with the current fluid level so that the absolute value of the difference and thus the volume difference of the brake fluid is determined. Next, in step S150, use the wear thickness of the front wheel or rear wheel friction plate determined in step S100, the volume difference determined in step S140, the corresponding diameter of the brake piston, etc. The wear thickness of the friction lining of the wheel is resistive sensor.

Next, in step S600, if the wear thickness of the friction lining determined in step S150 is greater than or equal to a predetermined value, then go to step S700. For example, in step S700, the indicators in the cockpit can be activated to issue visual and/or sound alarms to the driver, and/or some functions of the motor vehicle can be restricted, such as the speed at which the motor vehicle travels. Carry out restrictions, such as a maximum speed limit of 50 km/h, thereby arousing the driver's vigilance. If the wear thickness of the friction plate determined in step S150 is less than the predetermined value, then go to step S800, and send the test data to the instrument panel or the driver's mobile electronic device for display as regular status prompt information.

Therefore, it can be considered that the present application proposes another method for monitoring the loss of brake pads of a motor vehicle, wherein the motor vehicle includes a braking device acting on each wheel thereof, and the braking device has a function that can rotate together with the wheels. A brake disc mounted on the ground, and a friction plate that is non-rotatable relative to the wheel but can move linearly parallel to the axis of rotation of the wheel, the motor vehicle also includes a hydraulic brake drive device and a hydraulic brake drive device that is in fluid communication with the hydraulic brake drive device A brake fluid storage tank, the hydraulic brake driving device has a cylinder fixedly installed relative to the vehicle body, and a brake piston that can move linearly in the cylinder, and the brake piston of the hydraulic brake driving device can Brake fluid acting on the friction pads to provide hydraulic pressure to the friction pads to contact the brake disc via the brake fluid reservoir tank, the method comprising:

Stop the motor vehicle in a horizontal or substantially horizontal posture;

determining the current fluid level in the brake fluid storage tank;

determining the volume change of the brake fluid in the brake fluid storage tank based on the previously determined reference fluid level and the current fluid level;

In the case that the wear thickness of the friction lining equipped for the front wheel or the rear wheel is known, the volume change of the brake fluid in the brake fluid storage tank and the diameter of the brake piston of the brake device can be used to determine Correspondingly determine the wear thickness of the friction linings equipped with the rear or front wheels.

Optionally or additionally, when the wear thickness of the friction lining equipped for the front wheel or the rear wheel is known, the following formula is used to determine the wear thickness of the friction lining equipped for the rear wheel or the front wheel accordingly,

ΔL _X ＝(ΔV _L -πD ₀ ² ·ΔL ₀ -γ)/(πD _X ² ), where ΔL _X is the wear thickness of the friction lining to be determined, D ₀ is the friction lining corresponding to the known wear thickness The diameter of the brake piston, D _X is the diameter of the brake piston corresponding to the friction plate to be determined, ΔV _L is the volume change of the brake fluid, and γ is a non-zero empirical constant.

In addition, it can also be considered that the present application proposes another motor vehicle brake friction lining loss monitoring system. As shown in Figure 9, the system includes, for example:

a fluid level sensor 410 configured in the brake fluid storage tank 400;

Electronic control unit 100, described electronic control unit 100 is connected with described liquid level sensor 410 to obtain liquid level detection data, it is characterized in that, described electronic control unit 100 has:

The first module 2001, the first module 2001 generates an instruction to stop the motor vehicle in a horizontal or substantially horizontal posture;

A second module 2002, the second module 2002 generates an instruction to determine the current liquid level in the brake fluid storage tank;

The third module 2003, the third module 2003 generates an instruction to determine the brake fluid volume change ΔV _L in the brake fluid storage tank based on the previously determined reference fluid level and the current fluid level; and

The fourth module 2004, the fourth module 2004 generates the brake fluid volume change in the brake fluid storage tank, the The diameter of the brake piston of the above-mentioned brake device is used to determine the instruction of the wear thickness of the friction plate equipped for the rear wheel or front wheel accordingly.

The electronic control unit 100 also includes:

The fifth module 2005, the fifth module 2005 generates an instruction to operate the driving motor to move the piston driving member to a predetermined reference position after the motor vehicle is parked;

A sixth module 2006, which is generated after the fifth module to operate the drive motor again to move the piston driver from the reference position to its stop position in contact with the brake piston wherein the stop position corresponds to a parking brake position of the brake piston;

The seventh module 2007, the seventh module 2007 generates a method for determining the distance between the reference position and the stop position, and compares the determined distance with the previously determined reference distance to determine the wear of the tested friction plate thickness as an instruction for the known wear thickness.

The electronic control unit 100 also includes an eighth module 2008, the eighth module 2008 generates an instruction to remind the driver of the motor vehicle to replace the tested friction plate after the wear thickness of any one of the tested friction plates is lower than a predetermined value.

While specific embodiments of the application are described in detail herein, they are presented for purposes of illustration only and should not be considered limiting of the scope of the application. In addition, it should be clear to those skilled in the art that the various embodiments described in this specification can be used in combination with each other. Various alternatives, changes and modifications can be devised without departing from the spirit and scope of the application.

Claims (14)

1. A motor vehicle brake pad wear monitoring system, wherein the motor vehicle comprises a brake arrangement acting on each wheel thereof, the brake arrangement having a pad that is non-rotatable relative to the wheel but linearly displaceable parallel to the axis of rotation of the wheel, the motor vehicle further comprising a hydraulic brake drive arrangement having a linearly displaceable brake piston for acting on the pad to generate a braking force against the wheel, and a brake fluid reservoir tank (400) in fluid communication with the hydraulic brake drive arrangement, the system comprising:

a level sensor (410) disposed in the brake fluid reservoir tank (400);

-an electronic control unit (100), the electronic control unit (100) being connected to the liquid level sensor (410) to obtain liquid level detection data, characterized in that the electronic control unit (100) has:

a first module that generates instructions to cause the vehicle to stabilize in a horizontal or substantially horizontal attitude;

a second module that generates a command to determine a current liquid level within the brake fluid storage tank;

a third module that generates a determination of a brake fluid volume change (Δ V) in the brake fluid storage tank based on a predetermined reference fluid level and the current fluid level _L ) The instructions of (a); and

a fourth module, which generates a command for determining the wear thickness of the friction lining associated with the rear wheel or the front wheel using the volume change of the brake fluid in the brake fluid storage tank and the diameter of the brake piston of the hydraulic brake drive, if the wear thickness of the friction lining associated with the front wheel or the front wheel is known.

2. The system of claim 1, wherein the fourth module stores the following formula to determine a wear thickness of a friction plate provided for a rear wheel or a front wheel, respectively,

ΔL _X ＝(ΔV _L -πD ₀ ² ·ΔL ₀ -γ)/(πD _X ² ) Wherein, Δ L _X Is the wear thickness, D, of the friction lining to be determined ₀ Is in contact with the known wear thicknessDiameter of brake piston of brake device corresponding to friction plate of degree D _X Is the diameter, deltaV, of the brake piston of the brake device corresponding to the friction lining to be determined _L The volume change amount and gamma of the brake fluid in the brake fluid storage tank are non-zero empirical constants.

3. The system according to claim 1 or 2, wherein the reference level is a level in the brake fluid storage tank in a case where a newly installed friction plate of the same vehicle or all friction plates of the same vehicle are known in thickness and are stationary in a horizontal or substantially horizontal posture.

4. The system of claim 3, wherein the fourth module generates the command if no additional brake fluid is added to the brake fluid storage tank.

5. The system of claim 4, wherein a resistive sensor is provided in the friction plate of known wear thickness to determine the wear thickness of the friction plate.

6. A system according to claim 4, characterized in that the friction plate of known wear thickness is assigned an electronic parking brake (700) or an electromechanical brake (710) to determine the wear thickness of the friction plate.

7. The system of claim 6, wherein the electronic parking brake or the electromechanical brake comprises a driving motor and a piston driver driven by the driving motor to move linearly, and the brake piston is adapted to be driven by the piston driver to contact the friction plate to drive the friction plate to move when the vehicle brakes.

8. The system of claim 7, wherein the electronic control unit further comprises:

a fifth module that generates a command to operate the drive motor to move the piston driver to a predefined reference position after the vehicle has been parked;

a sixth module that generates a command after the fifth module to operate the drive motor again to move the piston driver from the reference position to a stopped position where it contacts the brake piston, wherein the stopped position corresponds to a parking brake position of the brake piston;

a seventh module that generates instructions to determine a distance between the reference position and the stop position and to compare the determined distance to a predetermined reference distance to determine a wear thickness of the friction plate under test as the known wear thickness.

9. The system of claim 8, wherein the reference distance is a distance that the piston driver is moved from a reference position to the stop position as determined when a parking brake is applied with a known thickness of a friction pad under test or with a friction pad under test that is entirely new.

10. The system of claim 9, wherein the known wear thickness of the friction plate under test is an absolute value of a difference between the determined distance and the reference distance.

11. The system of claim 7, wherein the electronic control unit further comprises an eighth module that generates an instruction to alert a driver of the vehicle to replace any one of the measured friction pads after the wear thickness of the measured friction pad is below a predetermined value.

12. The system as claimed in claim 11, wherein the electronic parking brake or the electronic mechanical brake further includes a speed reducing mechanism connected to an output shaft of the driving motor, and a linear moving mechanism driven by the speed reducing mechanism, the speed reducing mechanism being capable of providing a locking function of preventing the piston driver from being moved at will at the time of braking, the piston driver being linearly movable by the linear moving mechanism driven by the driving motor.

13. The system according to claim 12, wherein the linear movement mechanism is a threaded lead screw structure including a spindle connected to an output shaft of the reduction mechanism, and an outer surface of the spindle is formed with an external thread, and the piston driver is a screw member having an internal thread engageable with the external thread and being non-rotated when the spindle is rotated so as to be linearly movable back and forth in an axial direction of the spindle.

14. The system of claim 13, wherein the direction of movement of the piston driver to the reference position is opposite to the direction of movement of the piston driver from the reference position to the rest position.

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